In a standard batch-type prior-art thermomolding machine of the type described in U.S. Pat. No. 4,209,957 of Utzmann the foil is fed to a molding station that forms blisters in the foil that are filled in a succeeding filling station and then closed with a seal foil in a succeeding sealing station. The molding station is as a rule immediately downstream of a heating station in which the foil is warmed up to the temperature necessary for the formation of blisters, typically in a deep-drawing process. The heating can be done by contact with a heated platen or in a contact-free manner by passing the foil at a spacing past heaters in the heating station, a shield plate being movable between the heater elements and the foil to stop the heating. Such a machine is relatively easy to start and stop. Sections of the foil are heated in the heating station while stationary and then are shifted into the molding station where the shaping step takes place on, once again, a stationary workpiece. As the batchwise thermomolding machine is stopped and started a shield plate is moved into and out of the heating station to expose the foil, as needed, to the heat source.
This method is not applicable to a continuous-feed thermomolding machine, mainly because there is no cycling so that the foil pieces are continuously moving through the heating station. A piece that is insufficiently heated cannot be molded properly, so that at the start of operation the first few batches are unusable. In addition when a continuous-feed machine is stopped the foil piece in the heating station will cool off and will not have the required temperature when the machine is restarted.
German 198 50 143 of Bar and Gaus describes an apparatus for laminating together two workpieces, namely a glue layer and a seal. The two workpieces are heated with near infrared (NIR) emitters and their temperatures are monitored by pyrometers. This reference suggests that the NIR radiation be started and stopped in fractional seconds by the use of shutters, but this reference does not say how to avoid rejects with continuously moving workpieces and how to get the workpieces up to molding temperature when the machine is started.